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DiphenhydrAMINE

Classification

Antihistamine

Indications

ACP: Adjunct treatment of allergic reaction

Contraindications

Hypersensitivity to antihistamines
Neonates
Premature infants

Adult dosages

ACP: Allergic reaction

50 mg IV or 1 mg/kg to maximum of 50 mg

Pediatric Considerations And Dosing

Follow weight-based dosing

ACP: Allergic reaction

1 mg/kg IM/IV to maximum of 50 mg

Mechanism Of Action

Antihistamine with anticholinergic and sedating side effects. Appears to compete with histamine for receptors on effector cells.

Pharmocokinetics

Intramuscular:

Onset: rapid
Peak: unknown
Half-life: 1-4 hours
Duration: 4-6 hours

Adverse Effects

Most adverse effects are similar to other anticholinergic and antihistamine medications: mucosal membrane dryness, nervousness, irritability, and fatigue. Effects are dose-dependent.

Overdose

Symptoms of overdose are similar to those of atropine toxicity, and can include flushing, dilated pupils, hallucinations, confusion, ataxia, seizures, and loss of consciousness. Treatment is primarily supportive.

Warning And Precautions

DiphenhydrAMINE will not abort or terminate an allergic reaction that is progressing to anaphylaxis. It must not be used in place of EPINEPHrine in these patients.

DiphenhydrAMINE should be used with caution in patients with narrow-angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy, or bladder neck obstruction.

Drug Interactions

DiphenhydrAMINE can potentiate the effects of alcohol, benzodiazepines, and other CNS depressants. Drugs with anticholinergic properties, including tricyclic antidepressants, monoamineoxidase inhibitors, or other antihistamines, may also act synergistically.